1. Field of the Invention
The present invention relates to a composite material, and more particularly, to a method of manufacture of a metal matrix composite material having high integrity of microstructure available by high affinity between materials to compose the composite material and generation of intermetallic compounds therein.
2. Description of the Prior Art
In U.S. patent application Ser. No. 07/343,508 now U.S. patent application Ser. No. 07/646,460 assigned to the same assignee as the present application it has been proposed to manufacture a metal matrix composite material in which aluminum, aluminum alloy, magnesium or magnesium alloy forming a base matrix is reinforced by micro reinforcing elements such as short fibers, whisker, particles or mixture of these made of alumina, carbon silicate, nitrogen silicate or the like, by first forming a porous preform from such micro reinforcing elements, and then infiltrating the porous preform with a melt of the matrix material, wherein the novel concept resides in that a third powder material is incorporated as mixed in the reinforcing micro elements in the process of forming the porous preform, said third material being metal such as Ni, Fe, Co, Cr, Mn, Cu, Ag, Si, Mg, Al, Zn, Sn, Ti or an alloy or alloys of these metals when the matrix metal is Al or Al alloy, said third material being metal such as Ni, Cr, Ag, Al, Zn, Sn, Pb or alloy or alloys of these metals when the matrix metal is Mg Mg alloy, or said third material being oxide of metal such as W, Mo, Pb, Bi, V, Cu, Ni, Co, Sn, Mn, B, Cr, Mg Al or mixture of these when the matrix metal is Al, Al alloy, Mg or Mg alloy.
According to this method of manufacture, the third powder material expedites the infiltration of the molten matrix metal into the interstices of the porous preform not only by the good affinity or wettability of the third material itself with the molten matrix metal but also by increased fluidization of the molten matrix metal due to the heat generated by the reaction between the third powder material and the molten matrix metal.
In various experimental researches on this method, however, it was found that under certain manufacturing conditions there were formed micropores in the composite material. For example, when a composite material was manufactured by forming a preform consisting of 5% by volume SiC particles (10 microns average particle diameter), 30% by volume aluminum alloy powder (Al-12% Si, 40 microns average particle diameter) and 30% by volume pure copper powder (30 microns average particle diameter) and immersing the preform in a melt of aluminum alloy (JIS standard AC8A) at 575.degree. C. for 15 seconds, inspection of its section under the optical microscope revealed micropores in the composite structure which are guessed to have been caused by imperfect wetting of the aluminum alloy.